1. Field of the Invention
The present invention relates to a packing for sealing up a plurality of portions of an apparatus to be sealed, and in particular, to a packing used in, for example, a rotary change-over valve or the like of a liquid analyzer.
2. Description of the Prior Art
A particular flow-through type liquid analyzer, which is one example of a device to which a packing according to the present invention may be applied, is adapted so that the liquid flowing through a passage with bubbles interspersed between doses of liquid may be introduced into a detecting portion of the analyzer prior to the analysis, as disclosed in U.S. patent application Ser. No. 609,551, filed May 7, 1984, now abandoned. In order to introduce bubbles into the liquid flowing through the passage, a pump for pumping the liquid into the detecting portion, and a rotary type change-over valve are used. At least one of a plurality of inlet ports of this rotary type change-over valve is connected with a corresponding liquid-introducing tube, and the remaining inlet ports are connected to a source of air or an inert gas so that the starting end of a liquid passage to the detecting portion may be connected with an outlet port of the valve selectively connectable with these inlets ports. With this arrangement, the liquid doses and bubbles are alternately introduced into the liquid passage by the action of the pump and the selective connection of the outlet port of the change-over valve with an inlet port thereof.
In order to seal a space between an inlet port and the outlet port when the inlet port and outlet port are aligned, of such an analyzer apparatus, it has been attempted, for example, to use a separate O-ring for each of a large number of inlet ports and to subject ceramics and the like to mirror polishing.
Since use of the above described type change-over valve requires frequent selective changes in the connection of the outlet port with the inlet ports, not only a very good seal, but also easy maintenance to assure a continued good seal is required.
However, in the conventional means using O-rings a large number of O-rings is required and they are independent, respectively, so that it is difficult and has not been achieved to provide every O-ring with sufficient holding pressure to assure a sufficient seal. In addition, a rough surface is apt to be produced on the internal surface of the passage in the sealing portion. In particular, liquids tending to solidify in the passage such as blood, are apt to clog the passage and as a result, much difficulty and expense is encountered because the O-rings must be replaced and installed with great accuracy at the facings thereof.